Blood pressure is caused by the heart pumping blood through your body and the force it applies to the walls of arteries. Blood pressure constantly changes due to activity, diet, posture, emotional and physical state, and medication use. More:http://answers.ask.com/Arts/Other/what_causes_blood_pressure

Nov 24, 2009 There are many causes of high blood pressure, medications for other conditions. Find out which common drugs can raise blood pressure. Diphenhydramine ( Benadryl, Benadryl Allergy, Hydramine Cough Syrup, Excedrin